Changes imported from Abseil "staging" branch:

  - 20f4e7133d695e9a05e13ebdfd4d78da310b42b5 Remove the warning supressions -Wno-documentation and by Derek Mauro <dmauro@google.com>
  - e1bde85c0571673b1e7a88b9d45a393606ba7e6c Changed the optimized version of strings_internal::JoinAl... by Abseil Team <absl-team@google.com>
  - 746e6716b4c15be61547670d68d25a1c850d3954 Add missing absl:: qualification. by Alex Strelnikov <strel@google.com>
  - 4e5c18c488cbd49ca72b02911cf22d830d5a7f16 Internals change: Remove the ability to pass a custom met... by Greg Falcon <gfalcon@google.com>
  - 65d58107a5730d4b6468bbffc72bea2f980af826 Moved most common character case (ascii printable) out of... by Abseil Team <absl-team@google.com>
  - f031331cc55a3d57b9110e12c7cbe50ac3e2a04f Add missing copyright headers to a few source files. by Greg Falcon <gfalcon@google.com>
  - 6035a77af6fa951c536b42df4c710d16d1817aec Enable libstdc++'s memcmp optimization in absl::equal for... by Abseil Team <absl-team@google.com>
  - 73a665a4a10781e5d89f75a876ece7ad859f4116 Fix minor spelling error "hexidecimal". by Abseil Team <absl-team@google.com>

GitOrigin-RevId: 20f4e7133d695e9a05e13ebdfd4d78da310b42b5
Change-Id: Id8c18ebd331d096935052a6ab259ebe0e2ef13ae

20 files changed, 251 insertions, 114 deletions

diff --git a/absl/algorithm/algorithm.h b/absl/algorithm/algorithm.h
index 341b68b02038..3d6586439fe3 100644
--- a/absl/algorithm/algorithm.h
+++ b/absl/algorithm/algorithm.h
@@ -59,6 +59,18 @@ bool EqualImpl(InputIter1 first1, InputIter1 last1, InputIter2 first2,
          std::equal(first1, last1, first2, std::forward<Pred>(pred));
 }
 
+// When we are using our own internal predicate that just applies operator==, we
+// forward to the non-predicate form of std::equal. This enables an optimization
+// in libstdc++ that can result in std::memcmp being used for integer types.
+template <typename InputIter1, typename InputIter2>
+bool EqualImpl(InputIter1 first1, InputIter1 last1, InputIter2 first2,
+               InputIter2 last2, algorithm_internal::EqualTo /* unused */,
+               std::random_access_iterator_tag,
+               std::random_access_iterator_tag) {
+  return (last1 - first1 == last2 - first2) &&
+         std::equal(first1, last1, first2);
+}
+
 template <typename It>
 It RotateImpl(It first, It middle, It last, std::true_type) {
   return std::rotate(first, middle, last);
diff --git a/absl/base/exception_safety_testing_test.cc b/absl/base/exception_safety_testing_test.cc
index 20cbb435926a..1fc03861784e 100644
--- a/absl/base/exception_safety_testing_test.cc
+++ b/absl/base/exception_safety_testing_test.cc
@@ -1,3 +1,17 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #include "absl/base/internal/exception_safety_testing.h"
 
 #include <cstddef>
diff --git a/absl/base/internal/exception_safety_testing.cc b/absl/base/internal/exception_safety_testing.cc
index 32d904ed23fa..ab8d6c9fb4d0 100644
--- a/absl/base/internal/exception_safety_testing.cc
+++ b/absl/base/internal/exception_safety_testing.cc
@@ -1,3 +1,17 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #include "absl/base/internal/exception_safety_testing.h"
 
 #include "gtest/gtest.h"
diff --git a/absl/base/internal/exception_safety_testing.h b/absl/base/internal/exception_safety_testing.h
index 05bcd0ab59d6..a0127a8819fa 100644
--- a/absl/base/internal/exception_safety_testing.h
+++ b/absl/base/internal/exception_safety_testing.h
@@ -1,3 +1,17 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 // Utilities for testing exception-safety
 
 #ifndef ABSL_BASE_INTERNAL_EXCEPTION_SAFETY_TESTING_H_
diff --git a/absl/base/internal/exception_testing.h b/absl/base/internal/exception_testing.h
index 99a10734842b..07d7e8ee1ba6 100644
--- a/absl/base/internal/exception_testing.h
+++ b/absl/base/internal/exception_testing.h
@@ -1,3 +1,17 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 // Testing utilities for ABSL types which throw exceptions.
 
 #ifndef ABSL_BASE_INTERNAL_EXCEPTION_TESTING_H_
diff --git a/absl/base/internal/low_level_alloc.cc b/absl/base/internal/low_level_alloc.cc
index 962232433665..5f047a54389a 100644
--- a/absl/base/internal/low_level_alloc.cc
+++ b/absl/base/internal/low_level_alloc.cc
@@ -358,18 +358,15 @@ LowLevelAlloc::Arena::Arena(uint32_t flags_value)
 }
 
 // L < meta_data_arena->mu
-LowLevelAlloc::Arena *LowLevelAlloc::NewArena(int32_t flags,
-                                              Arena *meta_data_arena) {
-  ABSL_RAW_CHECK(meta_data_arena != nullptr, "must pass a valid arena");
-  if (meta_data_arena == DefaultArena()) {
+LowLevelAlloc::Arena *LowLevelAlloc::NewArena(int32_t flags) {
+  Arena *meta_data_arena = DefaultArena();
 #ifndef ABSL_LOW_LEVEL_ALLOC_ASYNC_SIGNAL_SAFE_MISSING
-    if ((flags & LowLevelAlloc::kAsyncSignalSafe) != 0) {
-      meta_data_arena = UnhookedAsyncSigSafeArena();
-    } else  // NOLINT(readability/braces)
+  if ((flags & LowLevelAlloc::kAsyncSignalSafe) != 0) {
+    meta_data_arena = UnhookedAsyncSigSafeArena();
+  } else  // NOLINT(readability/braces)
 #endif
-        if ((flags & LowLevelAlloc::kCallMallocHook) == 0) {
-      meta_data_arena = UnhookedArena();
-    }
+      if ((flags & LowLevelAlloc::kCallMallocHook) == 0) {
+    meta_data_arena = UnhookedArena();
   }
   Arena *result =
     new (AllocWithArena(sizeof (*result), meta_data_arena)) Arena(flags);
diff --git a/absl/base/internal/low_level_alloc.h b/absl/base/internal/low_level_alloc.h
index f3e8aa57f94f..3c15605bed35 100644
--- a/absl/base/internal/low_level_alloc.h
+++ b/absl/base/internal/low_level_alloc.h
@@ -93,15 +93,12 @@ class LowLevelAlloc {
     // DefaultArena(). Not supported on all platforms.
     kAsyncSignalSafe = 0x0002,
 #endif
-
-    // When used with DefaultArena(), the NewArena() and DeleteArena() calls
-    // obey the flags given explicitly in the NewArena() call, even if those
-    // flags differ from the settings in DefaultArena().  So the call
-    // NewArena(kAsyncSignalSafe, DefaultArena()) is itself async-signal-safe,
-    // as well as generatating an arena that provides async-signal-safe
-    // Alloc/Free.
   };
-  static Arena *NewArena(int32_t flags, Arena *meta_data_arena);
+  // Construct a new arena.  The allocation of the underlying metadata honors
+  // the provided flags.  For example, the call NewArena(kAsyncSignalSafe)
+  // is itself async-signal-safe, as well as generatating an arena that provides
+  // async-signal-safe Alloc/Free.
+  static Arena *NewArena(int32_t flags);
 
   // Destroys an arena allocated by NewArena and returns true,
   // provided no allocated blocks remain in the arena.
diff --git a/absl/base/internal/low_level_alloc_test.cc b/absl/base/internal/low_level_alloc_test.cc
index 2935760dad53..7c359f306115 100644
--- a/absl/base/internal/low_level_alloc_test.cc
+++ b/absl/base/internal/low_level_alloc_test.cc
@@ -84,7 +84,7 @@ static void Test(bool use_new_arena, bool call_malloc_hook, int n) {
   LowLevelAlloc::Arena *arena = 0;
   if (use_new_arena) {
     int32_t flags = call_malloc_hook ? LowLevelAlloc::kCallMallocHook : 0;
-    arena = LowLevelAlloc::NewArena(flags, LowLevelAlloc::DefaultArena());
+    arena = LowLevelAlloc::NewArena(flags);
   }
   for (int i = 0; i != n; i++) {
     if (i != 0 && i % 10000 == 0) {
diff --git a/absl/base/internal/pretty_function.h b/absl/base/internal/pretty_function.h
index 6be3936f7c24..01b0547bd08a 100644
--- a/absl/base/internal/pretty_function.h
+++ b/absl/base/internal/pretty_function.h
@@ -1,3 +1,17 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #ifndef ABSL_BASE_INTERNAL_PRETTY_FUNCTION_H_
 #define ABSL_BASE_INTERNAL_PRETTY_FUNCTION_H_
 
diff --git a/absl/copts.bzl b/absl/copts.bzl
index 22f3e54f39e2..fa111a00f15b 100644
--- a/absl/copts.bzl
+++ b/absl/copts.bzl
@@ -45,8 +45,6 @@ LLVM_FLAGS = [
     "-Wno-covered-switch-default",
     "-Wno-deprecated",
     "-Wno-disabled-macro-expansion",
-    "-Wno-documentation",
-    "-Wno-documentation-unknown-command",
     "-Wno-double-promotion",
     "-Wno-exit-time-destructors",
     "-Wno-extra-semi",
diff --git a/absl/debugging/leak_check.cc b/absl/debugging/leak_check.cc
index 30e7e8a85f09..e01e5f8c937e 100644
--- a/absl/debugging/leak_check.cc
+++ b/absl/debugging/leak_check.cc
@@ -1,3 +1,16 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
 // Wrappers around lsan_interface functions.
 // When lsan is not linked in, these functions are not available,
 // therefore Abseil code which depends on these functions is conditioned on the
diff --git a/absl/numeric/int128_test.cc b/absl/numeric/int128_test.cc
index 75fd6371040a..d674cb125f5e 100644
--- a/absl/numeric/int128_test.cc
+++ b/absl/numeric/int128_test.cc
@@ -175,8 +175,8 @@ TEST(Uint128, AllTests) {
   big_copy = big;
   EXPECT_EQ(big >> 73, big_copy >>= 73);
 
-  EXPECT_EQ(Uint128High64(biggest), std::numeric_limits<uint64_t>::max());
-  EXPECT_EQ(Uint128Low64(biggest), std::numeric_limits<uint64_t>::max());
+  EXPECT_EQ(absl::Uint128High64(biggest), std::numeric_limits<uint64_t>::max());
+  EXPECT_EQ(absl::Uint128Low64(biggest), std::numeric_limits<uint64_t>::max());
   EXPECT_EQ(zero + one, one);
   EXPECT_EQ(one + one, two);
   EXPECT_EQ(big_minus_one + one, big);
@@ -190,8 +190,8 @@ TEST(Uint128, AllTests) {
   EXPECT_EQ(zero - 1, biggest);
   EXPECT_EQ(high_low - one, low_high);
   EXPECT_EQ(low_high + one, high_low);
-  EXPECT_EQ(Uint128High64((absl::uint128(1) << 64) - 1), 0);
-  EXPECT_EQ(Uint128Low64((absl::uint128(1) << 64) - 1),
+  EXPECT_EQ(absl::Uint128High64((absl::uint128(1) << 64) - 1), 0);
+  EXPECT_EQ(absl::Uint128Low64((absl::uint128(1) << 64) - 1),
             std::numeric_limits<uint64_t>::max());
   EXPECT_TRUE(!!one);
   EXPECT_TRUE(!!high_low);
diff --git a/absl/strings/escaping.cc b/absl/strings/escaping.cc
index abe9e0aaacd9..fbc9f756315f 100644
--- a/absl/strings/escaping.cc
+++ b/absl/strings/escaping.cc
@@ -366,31 +366,31 @@ std::string CEscapeInternal(absl::string_view src, bool use_hex, bool utf8_safe)
   return dest;
 }
 
+/* clang-format off */
+constexpr char c_escaped_len[256] = {
+    4, 4, 4, 4, 4, 4, 4, 4, 4, 2, 2, 4, 4, 2, 4, 4,  // \t, \n, \r
+    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
+    1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1,  // ", '
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // '0'..'9'
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 'A'..'O'
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1,  // 'P'..'Z', '\'
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 'a'..'o'
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 4,  // 'p'..'z', DEL
+    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
+    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
+    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
+    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
+    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
+    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
+    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
+    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
+};
+/* clang-format on */
+
 // Calculates the length of the C-style escaped version of 'src'.
 // Assumes that non-printable characters are escaped using octal sequences, and
 // that UTF-8 bytes are not handled specially.
 inline size_t CEscapedLength(absl::string_view src) {
-  /* clang-format off */
-  constexpr char c_escaped_len[256] = {
-      4, 4, 4, 4, 4, 4, 4, 4, 4, 2, 2, 4, 4, 2, 4, 4,  // \t, \n, \r
-      4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
-      1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1,  // ", '
-      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // '0'..'9'
-      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 'A'..'O'
-      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1,  // 'P'..'Z', '\'
-      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 'a'..'o'
-      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 4,  // 'p'..'z', DEL
-      4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
-      4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
-      4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
-      4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
-      4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
-      4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
-      4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
-      4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
-  };
-  /* clang-format on */
-
   size_t escaped_len = 0;
   for (unsigned char c : src) escaped_len += c_escaped_len[c];
   return escaped_len;
@@ -409,41 +409,41 @@ void CEscapeAndAppendInternal(absl::string_view src, std::string* dest) {
   char* append_ptr = &(*dest)[cur_dest_len];
 
   for (unsigned char c : src) {
-    switch (c) {
-      case '\n':
-        *append_ptr++ = '\\';
-        *append_ptr++ = 'n';
-        break;
-      case '\r':
-        *append_ptr++ = '\\';
-        *append_ptr++ = 'r';
-        break;
-      case '\t':
-        *append_ptr++ = '\\';
-        *append_ptr++ = 't';
-        break;
-      case '\"':
-        *append_ptr++ = '\\';
-        *append_ptr++ = '\"';
-        break;
-      case '\'':
-        *append_ptr++ = '\\';
-        *append_ptr++ = '\'';
-        break;
-      case '\\':
-        *append_ptr++ = '\\';
-        *append_ptr++ = '\\';
-        break;
-      default:
-        if (!absl::ascii_isprint(c)) {
+    int char_len = c_escaped_len[c];
+    if (char_len == 1) {
+      *append_ptr++ = c;
+    } else if (char_len == 2) {
+      switch (c) {
+        case '\n':
           *append_ptr++ = '\\';
-          *append_ptr++ = '0' + c / 64;
-          *append_ptr++ = '0' + (c % 64) / 8;
-          *append_ptr++ = '0' + c % 8;
-        } else {
-          *append_ptr++ = c;
-        }
-        break;
+          *append_ptr++ = 'n';
+          break;
+        case '\r':
+          *append_ptr++ = '\\';
+          *append_ptr++ = 'r';
+          break;
+        case '\t':
+          *append_ptr++ = '\\';
+          *append_ptr++ = 't';
+          break;
+        case '\"':
+          *append_ptr++ = '\\';
+          *append_ptr++ = '\"';
+          break;
+        case '\'':
+          *append_ptr++ = '\\';
+          *append_ptr++ = '\'';
+          break;
+        case '\\':
+          *append_ptr++ = '\\';
+          *append_ptr++ = '\\';
+          break;
+      }
+    } else {
+      *append_ptr++ = '\\';
+      *append_ptr++ = '0' + c / 64;
+      *append_ptr++ = '0' + (c % 64) / 8;
+      *append_ptr++ = '0' + c % 8;
     }
   }
 }
diff --git a/absl/strings/escaping.h b/absl/strings/escaping.h
index 23444a987495..86f63aad7dc0 100644
--- a/absl/strings/escaping.h
+++ b/absl/strings/escaping.h
@@ -113,7 +113,7 @@ std::string Utf8SafeCEscape(absl::string_view src);
 // Utf8SafeCHexEscape()
 //
 // Escapes a 'src' std::string using C-style escape sequences, escaping bytes as
-// hexidecimal sequences, and passing through UTF-8 characters without
+// hexadecimal sequences, and passing through UTF-8 characters without
 // conversion.
 std::string Utf8SafeCHexEscape(absl::string_view src);
 
diff --git a/absl/strings/internal/str_join_internal.h b/absl/strings/internal/str_join_internal.h
index e73f1dde403d..c5fdc287cbab 100644
--- a/absl/strings/internal/str_join_internal.h
+++ b/absl/strings/internal/str_join_internal.h
@@ -31,13 +31,15 @@
 #ifndef ABSL_STRINGS_INTERNAL_STR_JOIN_INTERNAL_H_
 #define ABSL_STRINGS_INTERNAL_STR_JOIN_INTERNAL_H_
 
-#include <cassert>
+#include <cstring>
 #include <iterator>
 #include <memory>
 #include <string>
+#include <type_traits>
 #include <utility>
 
 #include "absl/strings/internal/ostringstream.h"
+#include "absl/strings/internal/resize_uninitialized.h"
 #include "absl/strings/str_cat.h"
 
 namespace absl {
@@ -202,28 +204,9 @@ std::string JoinAlgorithm(Iterator start, Iterator end, absl::string_view s,
   return result;
 }
 
-// No-op placeholder for input iterators which can not be iterated over.
-template <typename Iterator>
-size_t GetResultSize(Iterator, Iterator, size_t, std::input_iterator_tag) {
-  return 0;
-}
-
-// Calculates space to reserve, if the iterator supports multiple passes.
-template <typename Iterator>
-size_t GetResultSize(Iterator it, Iterator end, size_t separator_size,
-                     std::forward_iterator_tag) {
-  assert(it != end);
-  size_t length = it->size();
-  while (++it != end) {
-    length += separator_size;
-    length += it->size();
-  }
-  return length;
-}
-
-// A joining algorithm that's optimized for an iterator range of std::string-like
-// objects that do not need any additional formatting. This is to optimize the
-// common case of joining, say, a std::vector<std::string> or a
+// A joining algorithm that's optimized for a forward iterator range of
+// std::string-like objects that do not need any additional formatting. This is to
+// optimize the common case of joining, say, a std::vector<std::string> or a
 // std::vector<absl::string_view>.
 //
 // This is an overload of the previous JoinAlgorithm() function. Here the
@@ -236,20 +219,32 @@ size_t GetResultSize(Iterator it, Iterator end, size_t separator_size,
 // std::string to avoid the need to resize while appending. To do this, the iterator
 // range will be traversed twice: once to calculate the total needed size, and
 // then again to copy the elements and delimiters to the output std::string.
-template <typename Iterator>
+template <typename Iterator,
+          typename = typename std::enable_if<std::is_convertible<
+              typename std::iterator_traits<Iterator>::iterator_category,
+              std::forward_iterator_tag>::value>::type>
 std::string JoinAlgorithm(Iterator start, Iterator end, absl::string_view s,
                      NoFormatter) {
   std::string result;
   if (start != end) {
-    typename std::iterator_traits<Iterator>::iterator_category iterator_tag;
-    result.reserve(GetResultSize(start, end, s.size(), iterator_tag));
+    // Sums size
+    size_t result_size = start->size();
+    for (Iterator it = start; ++it != end;) {
+      result_size += s.size();
+      result_size += it->size();
+    }
+
+    STLStringResizeUninitialized(&result, result_size);
 
     // Joins strings
-    absl::string_view sep("", 0);
-    for (Iterator it = start; it != end; ++it) {
-      result.append(sep.data(), sep.size());
-      result.append(it->data(), it->size());
-      sep = s;
+    char* result_buf = &*result.begin();
+    memcpy(result_buf, start->data(), start->size());
+    result_buf += start->size();
+    for (Iterator it = start; ++it != end;) {
+      memcpy(result_buf, s.data(), s.size());
+      result_buf += s.size();
+      memcpy(result_buf, it->data(), it->size());
+      result_buf += it->size();
     }
   }
 
diff --git a/absl/strings/numbers.cc b/absl/strings/numbers.cc
index 31f07c72c949..b4140b3605bc 100644
--- a/absl/strings/numbers.cc
+++ b/absl/strings/numbers.cc
@@ -1,3 +1,17 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 // This file contains std::string processing functions related to
 // numeric values.
 
diff --git a/absl/strings/numbers_test.cc b/absl/strings/numbers_test.cc
index a705255c706d..5bb39ca9b5a9 100644
--- a/absl/strings/numbers_test.cc
+++ b/absl/strings/numbers_test.cc
@@ -1,3 +1,17 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 // This file tests std::string processing functions related to numeric values.
 
 #include "absl/strings/numbers.h"
diff --git a/absl/synchronization/internal/graphcycles.cc b/absl/synchronization/internal/graphcycles.cc
index 9bc9c8a0f00d..28ad172c01a2 100644
--- a/absl/synchronization/internal/graphcycles.cc
+++ b/absl/synchronization/internal/graphcycles.cc
@@ -56,8 +56,7 @@ static base_internal::LowLevelAlloc::Arena* arena;
 static void InitArenaIfNecessary() {
   arena_mu.Lock();
   if (arena == nullptr) {
-    arena = base_internal::LowLevelAlloc::NewArena(
-        0, base_internal::LowLevelAlloc::DefaultArena());
+    arena = base_internal::LowLevelAlloc::NewArena(0);
   }
   arena_mu.Unlock();
 }
diff --git a/absl/synchronization/mutex.cc b/absl/synchronization/mutex.cc
index b2aa743977ac..06a058cf710b 100644
--- a/absl/synchronization/mutex.cc
+++ b/absl/synchronization/mutex.cc
@@ -1,3 +1,17 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #include "absl/synchronization/mutex.h"
 
 #ifdef _WIN32
diff --git a/absl/time/clock.cc b/absl/time/clock.cc
index 59709dea0cf3..772f8525e84f 100644
--- a/absl/time/clock.cc
+++ b/absl/time/clock.cc
@@ -1,3 +1,17 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #include "absl/time/clock.h"
 
 #include "absl/base/attributes.h"